Proposed research will produce significant improvements in beam delivery technology enabling us to realize the full clinical advantage of heavy charged-particle beams. Specifically we will develop a raster-scanning beam spreading system that allows modulation of the spread Bragg peak over the target volume for the implementation of three-dimensional conformal therapy. The system will not only improve the therapeutic efficacy of the delivered beams, but also increase the versatility of the beam spreading system for varied clinical situations. To introduce the variable- modulation heavy charged-particle beams for therapy, we will develop new devices, as well as automated control and monitoring systems for safeguarding the patients treated using these devices. In particular, we will: (1) upgrade the power supply of the existing raster scanner magnets to allow modulation of the scanning speed; (2) develop and fabricate a variable collimator which automatically varies the size and shape of the radiation field; (3) develop and fabricate a large-area high-resolution ionization chamber to control and monitor the dose delivered by the raster scanning system; and (4) integrate the raster scanner with adjustable scan speed, the variable collimator and large-area high- resolution ionization chamber into one working system capable of performing three-dimensional conformal therapy through the development of control hardware and software, and expand the treatment control system for the raster-scanning beam spreading system to deliver radiation treatments ensuring accuracy, reliability, and patient safety. The results of the project will provide important and timely transfer of advanced technology to the scientific and medical community which is now attempting to implement in the clinical environment the heavy charged-particle radiotherapy developed in research institutions.